Rock drill



United States Patent O 3,498,390 ROCK DRILL Pekka Manno Salmi, Kuninkaankatu 36 A 25, Tampere, Finland Filed July 17, 1968, Ser. No. 745,537 Claims priority, application Finland, Jan. 16, 1968,

Int. Cl. B25d 9/04, 17/22; E21c 1/12 U.S. Cl. 173-105 Claims ABSTRACT OF THE DISCLOSURE The present invention concerns a rock drill comprising an axial, percussion piston which strikes the rear end of a drill rod, and a gear motor, operated by fluid under pressure, for imparting rotation to the drill socket located at the front end of the rock drill and to the drill rod inserted in the latter, and a gear transmission for reducing the speed of the motor to a value appropriate for the drill rod, the motor and transmission having been placed at the front end of the rock drill. The invention is characterized in that of the two gears of the gear motor one gear surrounds the percussion piston or the drill rod.

Previous art includes a rock drill having no separate motor for rotating the drill rod but which has a pawl and ratchet mechanism which rotates the drill rod through a given angle when the percussion piston strikes the rear end of the drill rod. The pawl and ratchet mechanism adds to the length of the rock drill so that the rock drill is inconvenient to use in narrow tunnels worked through rock. Furthermore, the pawl and ratchet mechanism causes in the rock drill stresses to which the percussion piston is subjected and which result in considerable Wear.

In order to avoid these drawbacks and in order to improve the performance, durability and reliability in operation, rock drills with separately induced rotation have been suggested before. A general shortcoming of such designs is the large bulk of the rotation-producing motor and of the transmission. Some such drills have the rotation-producing motor in their rear part, from where the rotational motion is transferred to the front end by a long shaft running on the outside of the cylinder. Such machines have the drawback of great length and large dimension in radial direction. In other drills, the rotation-producing motor and the transmission have been placed outside the drill at its front end, their drawback being, again, large radial dimension. When tunnels are being worked through rock, a bulky machine cannot be brought in close to the overhead face or walls of the gallery as a result of which substantial steps are caused by such drilling, which involve additional expenses e.g. due to concreting, bolting, etc. The length of the machine, again, determines the length of the feeding devices. A long machine requires a longer feeding device for the feeding length to remain the same. A long feeding device impedes, for instance, W-cut drilling in tunnels.

The aim of the present invention is to eliminate the drawbacks mentioned heretofore and to afford a rock drill the length and radial dimension of which are as small as possible. A rock drill according to the present invention, in which the gear motor has been placed at the front end of the rock drill. Is characterized in that one of the two gears of the gear motor surrounds the percussion piston or the drill rod. By this means the radial dimension of the gear motor is minimized.

A preferable embodiment of the invention is characterized in that the gear cooperating with the gear surrounding the percussion piston is in mesh with the lirst gear Patented Mar. 3, 1970 of the gear transmission, this latter gear surrounding the drill rod Yor the percussion piston. By this means also the radial dimension of the transmission can be minimized.

The invention will be described, for illustration, in the following with reference to the attached drawing, in which:

FIG. 1 shows a cross-sectional view of the front end of the rock drill, as taken along the line 1-1 in FIG. 2, and

FIG. 2 Shows a sectional view of the front end of the rock drill, along the line 11--11 in FIG. 2 and attened into a plane.

The rear end of the rock drill has been completely omitted in the drawings. The percussion piston 1 moves reciprocally in the cylinder 2 and in the sleeve 3 on its continuation. The front end of the percussion piston 1 strikes the rear end of the drill rod 4, which in this instance has a hexagonal cross section and has been inserted in the drill socket 5 presenting a similar cross section. The percussion piston is pierced by the pipe 6, through which flushing medium is supplied into the drill rod 4.

The gear motor, which imparts a rotational motion to the drill socket 5 and drill rod 4,`consists of the motor housing 7 and the gears 8 and 9. The gear 8 has been journalled on the sleeve 3, and the gear 9 is carried on bearings in the housing 7. Pressure medium, such as compressed air, is led into the housing 7 -by the duct 10, as can be seen from FIG. 1. From the opposite side of the gears 8 and 9 the pressure uid is discharged by a duct provided in the wall of the housing 7 (not shown in the ligure). The pressure uid may also be pressed in the opposite direction through the gear motor, which obviously makes the motor revolve in the opposite direction.

The right end in FIG. 2 of the gear 9 is in mesh with the rst double vgear 11 forming part of the transmission and which has been journalled on the body sleeve 12, in which the drill socket 5 has 4been mounted with force t. The other gear rim of the double gear 11 meshes with the right-hand (in FIG. 2) gear rim of another double gear 13 carried in bearings in the transmission housing 14. The left (in FIG. 2) gear train of the double gear 13 is in mesh with a gear 15 provided on the left end of the body sleeve 12 and thus, by mediation of the drill socket 5, rotating the drill rod 4. The ratio of the gear train 11, 13, 15 displayed in the drawing is about 10:1; that is if the speed of the motor gear 9 is 3000 r.p.m., then the drill rod 4 will revolve at 300 r.p.m.

Different embodiments of the invention may obviously vary within the claims stated below. For instance, the -motor and transmission gears must not necessarily be located, in the longitudinal direction of the rock drill, at the particular points shown in the drawing and it is obvious to anyone skilled in the art that these gears may be somewhat displaced in relation to each other. As shown in the drawing, the motor gear 8 and the rst double gear 11 of the transmission have been arranged to be concentric with the percussion piston 1 and drill rod 4, but it is obvious that they may be somewhat excentrically placed as well. As shown in the drawing, nylon rings have been used for axial bearings of the gears, but also other types of bearing can be contemplated.

What is claimed is:

1. Improvement in a rock drill, including an axial percussion piston which strikes the rear end of a drill rod, and a pressure Huid-operated gear motion serving to rotate the drill socket located at the front end of the rock drill and the drill rod inserted into' said socket, and a gear transmission for reducing the speed of the motor to a value appropriate for the drill rod, the motor and transmission having been placed at the front end of I 3 4 thel rock drill, wherein the improvement comprises in that` References Cited l of the two gears of the gear motor one gear surroundsth'e'" UNITED STATES PATENTS percussion piston or the drill rod.

l 2. Rock drill according to claim 1, characterized. in ligglln gg that the gear cooperating with the gear which surrounds 5 311661131 1/1965 Norman-:1111" 173 105 the percussion piston meshes with the rst gear of the 3,332,502 7 /1967 Vinnik 173 105 transmission, which gear surrounds the drill rod or the percussion piston. NILE C. BYERS, JR., Primary Examiner 

